Synthetic nucleosides such as 5-iodouracil and 5-fluorouracil have been used for the treatment of cancer for many years. Since the 1980's, synthetic nucleosides have also been a focus of interest for the treatment of HIV and hepatitis.
In 1981, acquired immune deficiency syndrome (AIDS) was identified as a disease that severely compromises the human immune system, and that almost without exception leads to death. In 1983, the etiological cause of AIDS was determined to be the human immunodeficiency virus (HIV). In 1985, it was reported that the synthetic nucleoside 3′-azido-3′-deoxythymidine (AZT) inhibits the replication of human immunodeficiency virus. Since then, a number of other synthetic nucleosides, including 2′,3′-dideoxyinosine (DDI), 2′,3′-dideoxycytidine (DDC), and 2′,3′-dideoxy-2′,3′-didehydrothymidine (D4T), have been proven to be effective against HIV. After cellular phosphorylation to the 5′-triphosphate by cellular kinases, these synthetic nucleosides are incorporated into a growing strand of viral DNA, causing chain termination due to the absence of the 3′-hydroxyl group. They can also inhibit the viral enzyme reverse transcriptase.
The success of various synthetic nucleosides in inhibiting the replication of HIV in vivo or in vitro has led a number of researchers to design and test nucleosides that substitute a heteroatom for the carbon atom at the 3′-position of the nucleoside. European Patent Publication No. 0 337 713 and U.S. Pat. No. 5,041,449, assigned to BioChem Pharma, Inc., disclose 2-substituted-4-substituted-1,3-dioxolanes that exhibit antiviral activity. U.S. Pat. No. 5,047,407 and European Patent Publication No. 0 382 526, also assigned to BioChem Pharma, Inc., disclose that a number of 2-substituted-5-substituted-1,3-oxathiolane nucleosides have antiviral activity, and specifically report that 2-hydroxymethyl-5-(cytosin-1-yl)-1,3-oxathiolane (referred to below as BCH-189) has approximately the same activity against HIV as AZT, with little toxicity.
It has also been disclosed that cis-2-hydroxymethyl-5-(5-fluorocytosin-1-yl)-1,3-oxathiolane (“FTC”) has potent HIV activity. Schinazi, et al., “Selective Inhibition of Human Immunodeficiency viruses by Racemates and Enantiomers of cis-5-Fluoro-1-[2-(Hydroxymethyl)-1,3-Oxathiolane-5-yl]-Cytosine” Antimicrobial Agents and Chemotherapy, November 1992, 2423-2431. See also U.S. Pat. Nos. 5,210,085; 5,814,639; and 5,914,331.
Another virus that causes a serious human health problem is the hepatitis B virus (referred to below as “HBV”). HBV is second only to tobacco as a cause of human cancer. The mechanism by which HBV induces cancer is unknown. It is postulated that it may directly trigger tumor development, or indirectly trigger tumor development through chronic inflammation, cirrhosis, and cell regeneration associated with the infection.
After a two to six month incubation period in which the host is unaware of the infection, HBV infection can lead to acute hepatitis and liver damage, that causes abdominal pain, jaundice, and elevated blood levels of certain enzymes. HBV can cause fulminant hepatitis, a rapidly progressive, often fatal form of the disease in which massive sections of the liver are destroyed.
Patients typically recover from acute hepatitis. In some patients, however, high levels of viral antigen persist in the blood for an extended, or indefinite, period, causing a chronic infection. Chronic infections can lead to chronic persistent hepatitis. Patients infected with chronic persistent HBV are most common in developing countries. By mid-1991, there were approximately 225 million chronic carriers of HBV in Asia alone, and worldwide, almost 300 million carriers. Chronic persistent hepatitis can cause fatigue, cirrhosis of the liver, and hepatocellular carcinoma, a primary liver cancer.
In western industrialized countries, high risk groups for HBV infection include those in contact with HBV carriers or their blood samples. The epidemiology of HBV is very similar to that of acquired immune deficiency syndrome, which accounts for why HBV infection is common among patients with AIDS or AIDS related complex. However, HBV is more contagious than HIV.
Both FTC and 3TC exhibit activity against HBV. Furman, et al., “The Anti-Hepatitis B Virus Activities, Cytotoxicities, and Anabolic Profiles of the (−) and (+) Enantiomers of cis-5-Fluoro-1-[2-(Hydroxymethyl)-1,3-oxathiolane-5-yl]-Cytosine” Antimicrobial Agents and Chemotherapy, December 1992, pp. 2686-2692; and Cheng, et al., Journal of Biological Chemistry, Volume 267(20), pp. 13938-13942 (1992). Other compounds that exhibit activity against HBV in humans include L-FMAU (Triangle Pharmaceuticals, Inc. under license from The University of Georgia Research Foundation and Yale University), and L-dT and L-dC (Idenix Pharmaceuticals, Inc.).
HCV is the major causative agent for post-transfusion and for sporadic non A, non B hepatitis (Alter, H. J. (1990) J. Gastro. Hepatol. 1:78-94; Dienstag, J. L. (1983) Gastro 85:439-462). Despite improved screening, HCV still accounts for at least 25% of the acute viral hepatitis in many countries (Alter, H. J. (1990) supra; Dienstag, J. L. (1983) supra; Alter M. J. et al. (1990a) J.A.M.A. 264:2231-2235; Alter M. J. et al (1992) N. Engl. J. Med. 327:1899-1905; Alter, M. J. et al. (1990b) N. Engl. J. Med. 321:1494-1500). Infection by HCV is insidious in a high proportion of chronically infected (and infectious) carriers who may not experience clinical symptoms for many years. The high rate of progression of acute infection to chronic infection (70-100%) and liver disease (>50%), its world-wide distribution and lack of a vaccine make HCV a significant cause of morbidity and mortality. Currently, there are three types of interferon and a combination of interferon and ribavirin used to treat hepatitis C. Selection of patients for treatment may be determined by biochemical, virologic, and when necessary, liver biopsy findings, rather than presence or absence of symptoms.
Interferon is given by injection, and may have a number of side effects including flu-like symptoms including headaches, fever, fatigue, loss of appetite, nausea, vomiting, depression and thinning of hair. It may also interfere with the production of white blood cells and platelets by depressing the bone marrow. Periodic blood tests are required to monitor blood cells and platelets. Ribavirin can cause sudden, severe anemia, and birth defects so women should avoid pregnancy while taking it and for 6 months following treatment. The severity and type of side effects differ for each individual. Treatment of children with HCV is not currently approved but is under investigation. While 50-60% of patients respond to treatment initially, lasting clearance of the virus occurs in only about 10-40% of patients. Treatment may be prolonged and given a second time to those who relapse after initial treatment. Re-treatment with bioengineered consensus interferon alone results in elimination of the virus in 58% of patients treated for one year. Side effects occur but the medication is usually well tolerated. Combined therapy (interferon and ribavirin) shows elimination of the virus in 47% after 6 months of therapy. Side effects from both drugs may be prominent.
A tumor is an unregulated, disorganized proliferation of cell growth. A tumor is malignant, or cancerous, if it has the properties of invasiveness and metastasis. Invasiveness refers to the tendency of a tumor to enter surrounding tissue, breaking through the basal laminas that define the boundaries of the tissues, thereby often entering the body's circulatory system. Metastasis refers to the tendency of a tumor to migrate to other areas of the body and establish areas of proliferation away from the site of initial appearance.
Cancer is now the second leading cause of death in the United States. Over 8,000,000 persons in the United States have been diagnosed with cancer, with 1,208,000 new diagnoses expected in 1994. Over 500,000 people die annually from the disease in this country.
Cancer is not fully understood on the molecular level. It is known that exposure of a cell to a carcinogen such as certain viruses, certain chemicals, or radiation, leads to DNA alteration that inactivates a “suppressive” gene or activates an “oncogene.” Suppressive genes are growth regulatory genes, which upon mutation, can no longer control cell growth. Oncogenes are initially normal genes (called prooncongenes) that by mutation or altered context of expression become transforming genes. The products of transforming genes cause inappropriate cell growth. More than twenty different normal cellular genes can become oncongenes by genetic alteration. Transformed cells differ from normal cells in many ways, including cell morphology, cell-to-cell interactions, membrane content, cytoskeletal structure, protein secretion, gene expression and mortality (transformed cells can grow indefinitely).
All of the various cell types of the body can be transformed into benign or malignant tumor cells. The most frequent tumor site is lung, followed by colorectal, breast, prostate, bladder, pancreas and then ovary. Other prevalent types of cancer include leukemia, central nervous system cancers, including brain cancer, melanoma, lymphoma, erythroleukemia, uterine cancer, and head and neck cancer.
Cancer is now primarily treated with one or a combination of three years of therapies: surgery, radiation and chemotherapy. Surgery involves the bulk removal of diseased tissue. While surgery is sometimes effective in removing tumors located at certain sites, for example, in the breast, colon and skin, it cannot be used in the treatment of tumors located in other areas, such as the backbone, or in the treatment of disseminated neoplastic conditions such as leukemia.
Chemotherapy involves the disruption of cell replication or cell metabolism. It is used most often in the treatment of leukemia, as well as breast, lung, and testicular cancer.
There are five major classes of chemotherapeutic agents currently in use for the treatment of cancer: natural products and their derivatives; anthacyclines; alkylating agents; antiproliferatives (also called antimetabolites); and hormonal agents. Chemotherapeutic agents are often referred to as antineoplastic agents.
The alkylating agents are believed to act by alkylating and cross-linking guanine and possibly other bases in DNA, arresting cell division. Typical alkylating agents include nitrogen mustards, ethyleneimine compounds, alkyl sulfates, cisplatin and various nitrosoureas. A disadvantage with these compounds is that they not only attach malignant cells, but also other cells which are naturally dividing, such as those of bone marrow, skin, gastrointestinal mucosa, and fetal tissue.
Antimetabolites are typically reversible or irreversible enzyme inhibitors, or compounds that otherwise interfere with the replication, translation or transcription of nucleic acids.
Several synthetic nucleosides have been identified that exhibit anticancer activity. A well known nucleoside derivative with strong anticancer activity is 5-fluorouracil. 5-Fluorouracil has been used clinically in the treatment of malignant tumors, including, for example, carcinomas, sarcomas, skin cancer, cancer of the digestive organs, and breast cancer. 5-Fluorouracil, however, causes serious adverse reactions such as nausea, alopecia, diarrhea, stomatitis, leukocytic thrombocytopenia, anorexia, pigmentation and edema. Derivatives of 5-fluorouracil with anti-cancer activity have been described in U.S. Pat. No 4,336,381, and in Japanese patent publication Nos. 50-50383, 50-50384, 50-64281, 51-146482, and 53-84981.
U.S. Pat. No. 4,000,137 discloses that the peroxidate oxidation product of inosine, adenosine or cytidine with methanol or ethanol has activity against lymphocytic leukemia.
Cytosine arabinoside (also referred to as Cytarabin, araC, and Cytosar) is a nucleoside analog of deoxycytidine that was first synthesized in 1950 and introduced into clinical medicine in 1963. It is currently an important drug in the treatment of acute myeloid leukemia. It is also active against acute lymphocytic leukemia, and to a lesser extent, is useful in chronic myelocytic leukemia and non-Hodgkin's lymphoma. The primary action of araC is inhibition of nuclear DNA synthesis. Handschumacher, R. and Cheng, Y., “Purine and Pyrimidine Antimetabolites” Cancer Medicine, Chapter XV-1, 3rd Edition, Edited by J. Holland, et al., Lea and Febigol, publishers.
5-Azacytidine is a cytidine analog that is primarily used in the treatment of acute myclocytic leukemia and myelodysplastic syndrome.
2-Fluoroadenosine-5′-phosphate (Fludara, also referred to as FaraA)) is one of the most active agents in the treatment of chronic lymphocytic leukemia. The compound acts by inhibiting DNA synthesis. Treatment of cells with F-araA is associated with the accumulation of cells at the G1/S phase boundary and in S phase; thus, it is a cell cycle S phase-specific drug. Incorporation of the active metabolite, F-araATP, retards DNA chain elongation. F-araA is also a potent inhibitor of ribonucleotide reductase, the key enzyme responsible for the formation of dATP.
2-Chlorodeoxyadenosine is useful in the treatment of low grade B-cell neoplasms such as chronic lymphocytic leukemia, non-Hodgkins' lymphoma, and hairy-cell leukenia.
In designing new nucleosides, there have been a number of attempts to incorporate a fluoro substituent into the carbohydrate ring of the nucleoside. Fluorine has been suggested as a substituent because it might serve as an isopolar and isosteric mimic of a hydroxyl group as the C—F bond length (1.35 Å) is so similar to the C—O bond length (1.43 Å) and because fluorine is a hydrogen bond acceptor. Fluorine is capable of producing significant electronic changes in a molecule with minimal steric perturbation. The substitution of fluorine for another group in a molecule can cause changes in substrate metabolism because of the high strength of the C—F bond (116 kcal/mol vs. C—H=100 kcal/mol).
A number of references have reported the synthesis and use of 2′-arabinofluoro-nucleosides (i.e., nucleosides in which a 2′-fluoro group is in the “up”-configuration). There have been several reports of 2-fluoro-β-D-arabinofuranosyl nucleosides that exhibit activity against hepatitis B and herpes. See, for example, U.S. Pat. No. 4,666,892 to Fox, et al.; U.S. Pat. No. 4,211,773 to Lopez, et al; Su, et al., Nucleosides. 136. Synthesis and Antiviral Effects of Several 1-(2-Deoxy-2-fluoro-β-D-arabinofuranosyl)-5-alkyluracils. Some Structure-Activity Relationships, J. Med. Chem., 1986, 29, 151-154; Borthwick, et al., Synthesis and Enzymatic Resolution of Carbocyclic 2′-Ara-fluoro-Guanosine: A Potent New Anti-Herpetic Agent, J. Chem. Soc., Chem. Commun, 1988; Wantanabe, et al., Synthesis and Anti-HIV Activity of 2′-“Up”-Fluoro Analogues of Active Anti-Aids Nucleosides 3′-Azido-3′-deoxythymidine (AZT) and 2′,3′-deoxythymidine (AZT) and 2′,3′-dideoxycytidine (DDC), J. Med. Chem. 1990, 33, 2145-2150; Martin, et.al., Synthesis and Antiviral Activity of Monofluoro and Difluoro Analogues of Pyrimidine Deoxyribonucleosides against Human Immunodeficiency Virus (HIV-1), J. Med. Chem. 1990, 33, 2137-2145; Sterzycki, et al., Synthesis and Anti-HIV Activity of Several 2′-Fluoro-Containing Pyrimidine Nucleosides, J. Med. Chem. 1990, as well as EPA 0 316 017 also filed by Sterzycki, et al.; and Montgomery, et al., 9-(2-Deoxy-2-fluoro-β-D-arabinofuranosyl)-guanine: A Metabolically Stable Cytotoxic Analogue of 2′-Deoxyguanosine. U.S. Pat. No. 5,246,924 discloses a method for treating a hepatitis infection that includes the administration of 1-(2′-deoxy-2′-fluoro-β-D-arabinofuranosyl)-3-ethyluracil), also referred to as “FEAU.” U.S. Pat. No. 5,034,518 discloses 2-fluoro-9-(2-deoxy-2-fluoro-β-D-arabino-furanosyl)adenine nucleosides which exhibit anticancer activity by altering the metabolism of adenine nucleosides by reducing the ability of the compound to serve as a substrate for adenosine. EPA 0 292 023 discloses that certain β-D-2′-fluoroarabinonucleosides are active against viral infections.
U.S. Pat. No. 5,128,458 discloses β-D-2′,3′-dideoxy-4′-thioribonucleosides as antiviral agents. U.S. Pat. No. 5,446,029 discloses that 2′,3′-didcoxy-3′-fluoro-nucleosides have anti-hepatitis activity.
European Patent Publication No. 0 409 227 A2 discloses certain 3′-substituted β-D-pyrimidine and purine nucleosides for the treatment of hepatitis B.
It has also been disclosed that L-FMAU (2′-fluoro-5-methyl-β-L-arabinofuranosyl-uracil) is a potent anti-HBV and anti-EBV agent. See Chu, et al., Use of 2′-Fluoro-5-methyl-β-L-arabinofuranosyluracil as a Novel Antiviral Agent for Hepatitis B Virus and Epstein-Barr Virus; Antimicrobial Agents and Chemotherapy, April 1995, 979-981; Balakrishna, et al., Inhibition of Hepatitis B Virus by a Novel L-Nucleoside, 2′-Fluoro-5-Methyl-β-L-arabinofuranosyl Uracil, Antimicrobial Agents and Chemotherapy, February 1996, 380-356; U.S. Pat. Nos. 5,587,362; 5,567,688; and 5,565,438.
U.S. Pat. Nos. 5,426,183 and 5,424,416 disclose processes for preparing 2′-deoxy-2′,2′-difluoronucleosides and 2′-deoxy-2′-fluoro nucleosides. See also Kinetic Studies of 2′,2′-difluorodeoxycytidine (Gemcitabine) with Purified Human Deoxycytidine Kinase and Cytidine Deaminase, BioChemical Pharmacology, Vol. 45 (No. 9) pages 4857-1861, 1993.
U.S. Pat. No. 5,446,029 to Eriksson, et al., discloses that certain 2′,3′-dideoxy-3′-fluoronucleosides have hepatitis B activity. U.S. Pat. No. 5,128,458 discloses certain 2′,3′-dideoxy-4′-thioribonucleosides wherein the 3′-substituent is H, azide or fluoro. WO 94/14831 discloses certain 3′-fluoro-dihydropyrimidine nucleosides. WO 92/08727 discloses β-L-2′-deoxy-3′-fluoro-5-substituted uridine nucleosides for the treatment of herpes simplex 1 and 2.
European Patent Publication No. 0 352 248 discloses a broad genus of L-ribofuranosyl purine nucleosides for the treatment of HIV, herpes, and hepatitis. While certain 2′-fluorinated purine nucleosides fall within the broad genus, there is no information given in the specification on how to make these compounds in the specification, and they are not among specifically disclosed or the preferred list of nucleosides in the specification. The specification does disclose how to make 3′-ribofuranosyl fluorinated nucleosides. A similar specification is found in WO 88/09001, filed by Aktiebolaget Astra.
European Patent Publication No. 0 357 571 discloses a broad group of β-D and α-D pyrimidine nucleosides for the treatment of AIDS which among the broad class generically includes nucleosides that can be substituted in the 2′ or 3′-position with a fluorine group. Among this broad class, however, there is no specific disclosure of 2′-fluorinated nucleosides or a method for their production.
European Patent Publication No. 0 463 470 discloses a process for the preparation of (5S)-3-fluoro-tetrahydro-5-[(hydroxy)methyl]-2-(3H)-furanone, a known intermediate in the manufacture of 2′-fluoro-2′,3′-dideoxynucleosides such as 2′-fluoro-2′,3′-dideoxycytidine.
U.S. Pat. Nos. 5,817,799 and 5,336,764 disclose β-D-2′-fluoroarabino-furanosyl nucleosides, and a method for their production, which are intermediates in the synthesis of 2′,3′-dideoxy-2′-fluoroarabinosyl nucleosides.
U.S. Pat. No. 4,625,020 discloses a method of producing 1-halo-2-deoxy-2-fluoroarabinofuranosyl derivatives bearing protective ester groups from 1,3,5-tri-O-acyl-ribofuranose.
U.S. Pat. No. 6,348,587 and International Publication No. WO 99/43691 disclose certain 2′-fluoronucleosides, including certain 2′-fluoro-2′,3′-dideoxy-2′,3′-didehydro-4′-((S, CH2 or CHF))-nucleosides, and their uses for the treatment of HIV, hepatitis (B or C), or proliferative conditions.
International Publication Nos. WO 01/90121 and WO 01/92282 disclose a wide variety of nucleosides for the treatment of HCV and flaviviruses and pestiviruses, respectively, including certain 2′-halo-2′,3′-dideoxy-2′,3′-didehydro-4′-(O, S, SO2 or CH2)-nucleosides.
The first example of 4′-thionucleosides was reported in 1964 by Reist et al., who synthesized the 4′-thio counterpart of naturally occurring adenosine (Reist, E. J.; Gueffroy, D. E.; Goodman, L. Synthesis of 4-thio-D-& L-ribofuranose and corresponding adenine nucleosides. J. Am. Chem. Soc. 1964, 86, 5658-5663).
A report by Young et al., emphasized the importance of this class of nucleosides, in which L-4′-thio-d4C analogues showed marked anti-HBV as well and anti-HIV activity (Young, R. J.; Shaw-Ponter, S.; Thomson, J. B.; Miller, J. A.; Cumming, J. G.; Pugh, A. W.; Rider, P. Synthesis and antiviral evaluation of enantiomeric 2′,3′-dideoxy- and 2′,3′-didehydro-2′,3′-dideoxy-4′-thionucleosides. Bioorg. Med. Chem. Lett. 1995, 5, 2599-2604).
Since then, several classes of 4′-thionucleosides have been reported, (Whistler, R. L.; Doner, L. W.; Nayak, U. G. 4-Thio-D-arabinofuranosylpyrimidine nucleosides. J. Org. Chem. 1971, 36, 108-110; Bobek, M.; Bloch, A.; Parthasarathy, R.; Whistler, R. L. Synthesis and biological activity of 5-fluoro-4′-thiouridine and some related nucleosides. J. Med. Chem. 1975, 18, 784-787), including 9-(4-thio-D-xylofuranosyl)adenine (Reist, E. J.; Fisher, L. V.; Gueffroy, E.; Goodman, L. Neighboring-group participation. Preparation of dithiopentose sugars via a thioacylonium ion intermediate. J. Org. Chem. 1968, 33, 189-192), 9-(4-thio-D-arabinofuranosyl)adenine (Reist, E. J.; Fisher, L. V.; Gueffroy, E.; Goodman, L. Neighboring-group participation. Preparation of dithiopentose sugars via a thioacylonium ion intermediate. J. Org. Chem. 1968, 33, 189-192), and 4′-thio-araC (Ototani, N.; Whistler, R. L. Preparation and antitumor activity of 4′-thio analogs of 2,2′-anhydro-1-β-D-arabinofuranosylcytosine. J. Med. Chem. 1974, 17, 535-537).
However, the difficulty of synthesizing optically pure 4′-thionucleosides has impaired additional syntheses of these analogues, and only a few examples have been known until recently (Fu, Y. -L.; Bobek, M. In Nucleic Aicd Chemistry; Townsend, L.; Tipson, R. S., Eds.; John Wiley & Sons: New York, 1978; pp 317-323). Moreover, biologically interesting 2′-deoxy-4′-thionucleosides had not been synthesized until Walker and Secrist independently reported the syntheses of pyrimidine 2′-deoxy-4′-thionucleosides in 1991 (Dyson, M. R.; Coe, P. L.; Walker, R. T. The synthesis and antiviral properties of E-5-(2-bromovinyl)-4′-thio-2′-deoxyuridine. J. Chem. Soc., Chem. Commun. 1991, 741-742; Dyson, M. R.; Coe, P. L.; Walker, R. T. The synthesis and antiviral activity of some 4′-thio-2′-deoxy nucleoside analogs. J. Med. Chem. 1991, 34, 2782-2786; Secrist, J. A.; Tiwari, K. N.; Riordan, J. M.; Montgomery, J. A. Synthesis and biological activity of 2′-deoxy-4′-thiopyrimidine nucleosides. J. Med. Chem. 1991, 34, 2361-2366), which were followed by an alternative synthesis of 2′-deoxy-4′-thionucleosides using the Sharpless asymmetric epoxidation (Uenishi, J.; Motoyama, M.; Nishiyama, Y.; Wakabayashi, S. Stereocontrolled preparation of cyclic xanthate—A novel synthetic route to 4-thiofuranose and 4′-thionucleoside. J. Chem. Soc., Chem. Commun. 1991, 1421-1422; Uenishi, J.; Takahashi, K.; Motoyama, M.; Akashi, H.; Sasaki, T. Syntheses and antitumor activities of D-2′-deoxy-4′-thio and L-2′-deoxy-4′-thio pyrimidine nucleosides. Nucleosides Nucleotides 1994, 13, 1347-1361), synthesis of 4′-thio-2′,3′-dideoxynucleosides (Secrist, J. A.; Riggs, R. M.; Tiwari, K. N.; Montgomery, J. A. Synthesis and anti-HIV activity of 4′-thio-2′,3′-dideoxynucleosides. J. Med. Chem. 1992, 35, 533-538), and the syntheses of 4′-thioarabinonucleosides (Secrist, J. A.; Tiwari, K. N.; Shortnacy-Fowler, A. T.; Messini, L.; Riordan, J. M.; Montgomery, J. A. Synthesis and biological activity of certain 4′-thio-D-arabinofuranosylpurine nucleosides. J. Med. Chem. 1998, 41, 3865-3871; Yoshimura, Y.; Watanabe, M.; Satoh, H.; Ashida, N.; Ijichi, K.; Sakata, S.; Machida, H.; Matsuda, A. A facile, alternative synthesis of 4′-thioarabinonucleosides and their biological activities. J. Med. Chem. 1997, 40, 2177-2183) as well as 2′-modified 2′-deoxy-4′-thiocytidines (Yoshimura, Y.; Kitano, K.; Yamada, K.; Satoh, H.; Watanabe, M.; Miura, S.; Sakata, S.; Sasaki, T.; Matsuda, A. A novel synthesis of 2′-modified 2′-deoxy4′-thiocytidines from D-glucose. J. Org. Chem. 1997, 62, 3140-3152). The synthesized 4′-thio-2′-deoxy, 4′-thio-2′,3′-dideoxy and 4′-thioarabino nucleosides have shown to have potent anti-herpes, anti-HIV and anti-cytomegalovirus activities, respectively, and some analogues, especially 4′-thiothymidine and 2′-deoxy-4′-thiocytidine, have exhibited potent cytotoxicity. The 4′-thionucleosides are usually resistant to hydrolytic cleavage of glycosyl linkage catalyzed by nucleoside phosphorylase, which is one of the advantages of 4′-thionucleosides compared with several metabolically unstable “4′-oxy” antiviral agents which are substrates for nucleoside phosphorylase (Parks, R. E., Jr.; Stoeckler, J. D.; Cambor, C.; Savarese, T. M.; Crabtree, G. W.; Chu, S. -H. In Molecular Actions and Targets for Cancer Chemotherapeutic Agents; Sartorelli, A. C., Lazo, J. S., Bertino, J. R., Eds.; Academic Press: New York, 1981; pp 229-252; Desgranges, C.; Razaka, G.; Rabaud, M.; Bricaud, H.; Balzarini, J.; De Clercq, E. Phosphorolysis of (E)-5-(2-bromovinyl)-2′-deoxyuridine (BVDU) and other 5-substituted-2′-deoxyuridines by purified human thymidine phosphorylase and intact blood-platelets. Biochem. Pharmacol. 1983, 32, 3583-3590; Samuel,. J.; Gill, M. J.; Iwashina, T.; Tovell, D. R.; Tyrrell, D. L.; Knaus, E. E.; Wiebe, L. I. Pharmacokinetics and metabolism of E-5-(2-[I-131]iodovinyl)-2′-deoxyuridine in dogs. Antimicrob. Agents Chemother. 1986, 29, 320-324).
Even though 4′-thionucleosides have recently received considerable attention as potential antiviral agents, their 2′,3′-unsaturated analogues have not been well investigated probably because of the synthetic difficulties. The known synthetic methods employ either nucleophilic attack of dimesylate by disulfide anion (Yoshimura, Y.; Watanabe, M.; Satoh, H.; Ashida, N.; Ijichi, K.; Sakata, S.; Machida, H.; Matsuda, A. A facile, alternative synthesis of 4′-thioarabinonucleosides and their biological activities. J. Med. Chem. 1997, 40, 2177-2183; Yoshimura, Y.; Kitano, K.; Yamada, K.; Satoh, H.; Watanabe, M.; Miura, S.; Sakata, S.; Sasaki, T.; Matsuda, A. A novel synthesis of 2′-modified 2′-deoxy-4′-thiocytidines from D-glucose. J. Org. Chem. 1997, 62, 3140-3152), ring closure of dithioacetal (Secrist, J. A.; Tiwari, K. N.; Shortnacy-Fowler, A. T.; Messini, L.; Riordan, J. M.; Montgomery, J. A. Synthesis and biological activity of certain 4′-thio-D-arabinofuranosylpurine nucleosides. J. Med. Chem. 1998, 41, 3865-3871) or reductive cyclization of thioacetic acid ester (Secrist, J. A.; Riggs, R. M.; Tiwari, K. N.; Montgomery, J. A. Synthesis and anti-HIV activity of 4′-thio-2′,3′-dideoxynucleosides. J. Med. Chem. 1992, 35, 533-538).
The stereoselective synthesis of the β-L-2′-F4′-Sd4C, which showed potent anti-HIV activity (EC50 0.12 μM) in human peripheral blood monomuclear (PBM) cells, was reported (Choi, Y.; Choo, H.; Chong, Y.; Lee, S.; Olgen, S.; Schinazi, R. F.; Chu, C. K. Synthesis and potent anti-HIV activity of L-2′,3′-didehydro-2′,3′-dideoxy-2′-fluoro4′-thiocytidine. Org. Lett. 2002, 4, 305-307).
In light of the fact that acquired immune deficiency syndrome, AIDS-related complex, hepatitis B virus and hepatitis C virus have reached epidemic levels worldwide, and have tragic effects on the infected patient, there remains a strong need to provide new effective pharmaceutical agents to treat these diseases that have low toxicity to the host. Further, there is a need to provide new antiproliferative agents,
Therefore, it is an object of the present invention to provide a method and composition for the treatment of human patients or other host animals infected with HIV.
It is another object of the present invention to provide a method and composition for the treatment of human patients infected with hepatitis B or C.
It is a further object of the present invention to provide new antiproliferative agents.
It is still another object of the present invention to provide a new process for the preparation of β-halonucleosides of the present invention.